A wide band SAW filter using slanted transducer fingers has an advantage that the insertion loss is small, etc, with respect to a SAW filter using the apodizing method or dispersion type electrodes. However, on the other hand, it has a great disadvantage that the central pass band characteristics are adequately flat, but are generally inclined with frequency.
As a method for solving the problem, heretofore there have been proposed a method, by which corrections are effected in an external circuit, described in an article entitled "Wide-Band Linear Phase SAW Filter Design Using Slanted Transducer Fingers" IEEE Trans. on Sonics & Ultrasonics, SU-29, No. 6, pp 244-228, (July, 1982) by C. K. Campbell, et al., a method, by which corrections are effected by weighting a number of pairs of electrodes, described in an article entitled "Wide Band Surface Acoustic Wave Filter Using Slanted Transducer Fingers Weighting a Number of Pairs of Electrodes" Technical Reports of the Electronic Communication Society of Japan, U.S. 84-31 (September, 1984) by Yoshikawa, et al.,
These methods have a drawback that the pass band characteristics of the SAW filter are also similarly inclined in the frequency domain.